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What performance issues/symptoms can a pilot expect while taking off above MTOW?
Lately I've been flying a Cessna 162 Skycatcher, primary as a cheap way to build time towards the Instrument Cross Country requirement and my glider club's hours requirement to tow gliders.
One issue with the 162 is it's relatively low Useful Load.  Here are some figures relevant to my question:

Maximum Takeoff Weight: 1324
Equipped Empty Weight: 857
Useful Load: 467
Weight of full fuel: 24*6 = 144
Weight of 3/4 fuel: 18*6 = 108
My Weight: 215
Max Weight of passenger full fuel: 108.24
Max Weight of passenger 3/4 fuel: 144.24

Note: All Weights above are in pounds(lbs).
Because weight is an issue with this plane and almost any passenger I would consider bringing along, there is a diagram in the FBO's flight book that can be shown to the person fueling that depicts points inside the tanks that denote full, 3/4, 1/2, etc:

Last week, I did a flight with a 130 pound passenger.  On the first refueling I was sure to show this diagram to the person filling to ensure he only filled to 3/4.  I generally make it a habit to inspect the tanks after fueling to ensure they have not gone over the asked for amount.  Takeoff was normal with no noticeable degradation in performance.  Note: the fuel gauges in the 162 tend to show the same value whether the tanks are full or 3/4 full, with no noticeable decrease until until values go below 3/4.
We then proceeded to fly roughly 1.5 hours to another airport.  At that airport, I went through the same routine but (in a hurry of course, isn't that how most mistakes are made!) I did not follow up to ensure he had not "overfilled" the tanks.  On takeoff, I noted a notable (though by no means catastrophic) degradation in performance:

I needed more runway to rotate.
I could not climb above 55kts (Vx/Vy in the 162 are 57/62).

As I was able to climb at a safe enough airspeed, things seemed to stabilize and I had no other issues, I chose to proceed with the return flight.  Performance for the rest of the flight was fine with no extra RPM needed to cruise or do later climbs.
It wasn't until I was thinking about it later that it occurred to me that the refueler might have filled my tanks to full.
So my question is, do these symptoms sound indicative of being overweight?  Or, more generally,
What performance issues can a pilot expect while taking off above MTOW?
Note: I have reviewed several questions related to this, including:

Can a commercial airliner be too heavy to take off?
Does weight and balance of an airplane matter more on takeoff?
Questions tagged with weight-and-balance

However, I didn't find a question dealing specifically with the performance degradation felt by a pilot taking off above MTOW.
Update
After thinking on this a bit more, reading some of the answers and talking it over with my daughter (the passenger mentioned and a pilot in her own right), I'm leaning towards a different conclusion.  Since I was first checked out in the 162 last winter, this was the first time I'd had a passenger.  My first takeoff was from KJYO (5500 feet runway length / 390 ft elevation), whereas my second was from Eagles Nest (W13) (2004 ft runway length / 1436 ft elevation).  My new theory is that what I felt on the second takeoff was the added weight I wasn't used to since I've flown the previous 20+ flights alone.  I believe I didn't notice this as much on my first takeoff because I had much more runway to work with.
Nonetheless, I think the question and answers are still relevant/useful.

From personal experience of me (~200 lbs) and a flight instructor who was at least 250, in a tired old 150,  departing Stead where the eastbound runway drops about 100 ft to a (usually) dry lake bed, you can expect to look back and see dirt behind you :-)

The MTOW you list for the 162 puts it 4 lbs over the LSA limit of 1320 lbs. Is there some reason for that?

Firstly, you did goof up by not checking what the refueler did. Your life depends on that fuel, and in light aircraft the gauges are notoriously unreliable. We've probably all done it but we shouldn't - always check!
However going off your figures you might have been what, 20 pounds overweight? That shouldn't cause such a massive decrease in performance. MTOW isn't an on/off switch. It's a point that has been selected as the maximum allowable limit - with a safety margin built in. You should never exceed MTOW even by a bit, but if you do you will (hopefully) live to see your kids birthday thanks to that margin.
I've flown a C172 right at MTOW (actually about 5kg under but close enough). Acceleration is slow, meaning you use more runway. Rotation actually feels normal thanks to ground effect, but once you leave that you notice a degraded climb performance. If you're over MTOW these effects are the same but amplified. If you are very overweight, you will climb in ground effect but will struggle to go much higher than 20-30ft.
As for your flight though, it could have been affected by a tailwind or high temperature/low atmospheric pressure. What was the temperature like on the second leg? Vy will theoretically get you the best climb rate even above MTOW so it doesn't make sense that you could climb below but not at that speed. Maybe there was something localised affecting the ASI, or, if I may be so bold, your technique on the day wasn't 100% :)

"You should never exceed MTOW even by a bit" <-- that's not true at all. People exceed MTOW all the time for any number of reasons, sometime in accordance with and other times in violation of the regs. Sometimes it's just based on the class or the country the plane is certified in. MTOW is a decent guess from the manufacturer, designed to give acceptable performance based on a wide variety of situations. It's not a magic number. Contrast that to balance, which is far, far more critical.

It's possible you were overweight, a longer takeoff roll and degraded climb performance are definitely symptoms, however there are other possibilities as well, for instance a higher density altitude. Assuming you are in the northern hemisphere and therefore in summer, a couple of hours can make a big difference temperature-wise, and therefore to your density altitude can be much more than you might expect. Let's compare a sea level airfield at standard pressure when it's 50 degrees F (11C) versus 90 degrees F (32C), at 50F the DA is about 450ft, at 90F it's closer to 3000ft (dew point dependent). An airfield at 1500ft elevation at standard pressure and 90F temperature would be 4700ft density altitude. A high density altitude also makes for a much longer takeoff roll and decreases climb performance.
It's possible you may have been both a shade overweight in hot and/or high conditions, which would make for an uncomfortable beginning of the flight.

Yeah...its my bad for not mentioning it in my post, but I did consider density altitude.  No significant difference between the first take off and the second.  Though the second takeoff was a bit later in the day, which would normally have been warmer, the airport had had some rain, which actually kept the temperature pretty stable.  The other component of DA, atmospheric pressure had no significant change.

@bclarkreston the second airport is also at a 1040 feet higher elevation, that should be noticeable.

@DeltaLima quite right, but do you think 1k feet would be as noticeable as I've described it?

Provided that you don't run out of runway, you will probably get unstuck, but perhaps then you won't be able to fly above ground effect. The MTOW figure has usually a considerable margin of tolerance, but a pilot should follow the rules exactly, and consider it an absolute limit...

Yes, MTOW is there to save your neck, BUT - there will come a time when you decide that it is necessary to exceeed/ignore it, for whatever reason seems good to you. Each situation needs careful analysis. Understand that MTOW changes with temp / density alt/wind/Rw length /rw slope/even safety margin inherent in the a/c design, such as power reserve amd wing section polar. We are talking extreme situations, such as PNG mountain strips, <1700 length, 5000'high, 25 C, and passengers determined to fill by volume. Overweight of 20% useful load can usually be accomodated by technique, you need to know flight in ground effect, use of thermals and, of course, fhe terrain ahead. Older designs often have a bettter margin than more modern types.  DC3 have been known to get away with 200% of useful load, a popular usa light 2/4 seater was fatally overweight, inquest found that it would have been overweight with pilot and zero fuel, not the pilot, 3pax, luggage and full fuel they attempted T/O with. I have flown a seriously OW Aztec, but I had lomg sealed strips both ends and leaving the high country behind. I didn't calculate TOW, didn't want to frighten myself.
The Aztec wasa great bush type.


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What causes the "growl" of some large turbofans at takeoff thrust?
There are some (all?) large turbofans which emit a distinct "growl" (some people call it a "buzzsaw" sound) at takeoff thrust. What causes it? I've seen it explained (as in this question) as the fan blade tips going trans sonic, but it doesn't account for the pitch, or so I believe. A main fan has something like 20 or 30 blades, and must be spinning at several thousand RPM at takeoff power (maybe on the order of 4,000); a blade tip would then be passing a given fixed point at around 80,000 (or more) per minute or 1,300 (or more) per second.
The musical middle C is only around 260 Hz, so any blade noise should sound like a high-pitched whine, not a low-pitched growl. You can often hear "beat" sounds due to two or more engines running at almost the same speed, but the buzzsaw growl is distinctly different. So what causes that sound at that pitch?

This is a very sciencey question, not strictly an aviation one, so I believe it should be on physics.se

Possible duplicate of What is the buzzing noise generated by the engines in this 777 takeoff video?

@Ben Aviation is actually based on science, physics, mathematics, aerodynamics, material science, aeroelasticity,  structures engineering, and a few others.

@Koyovis of course, but at its core this question is about sound physics, which is a subject covered in physics.se rather than this site.

@Ben Just because something is on topic somewhere else, does not mean it's off-topic here. It also depends on the kind of answer you want (you'll get a very different perspective at physics.SE).

There is a wide range of harmonics generated by the fan, descending all the way into the lower sound spectrum. This article is about sound insulation of a turbofan shroud, and contains sound measurements of an actual turbofan in a ground installation at full TO power:

The article seems to be Google translated into English from Russian, but the observations made are very valid:

At power regimes with Mach number M>1 at the periphery of blade wheel there is a well- observed shock wave noise appeared on harmonics of rotor frequency that could be seen at fre- quency range between the first rotor frequency and fan BPF. Shock wave noise has a high sound power level due to the used lemniscate inlet duct without lining and waisting.

We presume that "waisting" is meant as in: application of a varying cross-sectional shape (waist). The blue lines in the plot are the harmonics of the rotor frequency. There are 16 of them in the first 1200 Hz, in a linear scale this implies that the distance between blue lines is 75 Hz.
Significant sound peaks can be found at intervals of 75 Hz, immediately starting at the first harmonic line of 75 Hz. Note that the fan Blade Passing Frequency is at around 2,500 Hz, but that the frequency spectrum below the fan BPF is quite densely populated. The dominant sound that is observed on ground from an aircraft turbofan is of course dependent upon the position, distance, inlet shape, acoustic insulation measures etc etc. It makes a lot of sense if most sound insulation efforts are invested in the loudest spectrum, and that the low buzz sounds are regarded as a low priority for suppression since they are not very disturbing.

"Buzzsaw noise", as commonly defined, is caused by the shock waves from the trans-sonic fan blade tips, as described in the answer by @Koyovis, as well as the linked answer.
Your question seems to focus on the low frequency component of the sound, and you correctly point out that fan blade passing frequency will be on the order of 1 kHz.
There is another source of noise generated by the engine that can often be heard in the cabin, and this is caused by the vibration of the fan rotor.  Whenever the fan is not perfectly balanced (and it is never perfect), the unbalance will cause a vibration at the rotation frequency of the fan.  This is almost certainly the 75 Hz fundamental tone in the article linked by @Koyovis.  The rotor speed varies with the size of the engine, 45 Hz for a big one like on a 777, up to 100 - 200 Hz for small regional jets.
This vibration energy is transmitted as structural vibration through the engine structure, through the pylon and the wing, and then causes the fuselage itself to vibrate at that frequency.  This causes the interior of the cabin to become a giagantic loudspeaker, at the rotor frequency.
Engine and aircraft manufacturers attempt to control this noise by keeping the engines well balanced, and trying to minimize the amount of power transmitted through the wing.

But again, vibration due to imbalance ought to be sinusoidal at the same frequency as the shaft rotation speed (45Hz, as you say). That would be perceived not as a "buzzsaw" sound, but more of a rumble, woudn't it?

Vibration due to imbalance is sinusoidal at the same frequency of the shaft rotation, yes.  But I don't think that would be perceived as a "rumble".  That may be subjective though.  Go to http://www.szynalski.com/tone-generator/ and generate a 75 Hz sine wave (or as low as your sound system will go).  Does that sound like a rumble to you?

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COMAC C919 engine

COMAC C919 has been dubbed as one of the biggest successes in the Chinese aviation industry as this is the first narrow-body airliner capable of long-distance flight. This is important for China as this will save China an enormous amount of foreign currency in the decades to come.
However, this airliner uses an engine from CFM International, a joint venture between the American company GE and the French company Safran.
Why does China depend on US engines when the USA can put sanctions at any time if they see any competition in their existing market, and what is their backup plan for engines?

GE doesn't seem to like Boeing that much so the price should be quite attractive to the Chinese. In fact I think this is true for the entire project that they used so many US parts, because all US suppliers hates Boeing and are willing to give a second buyer at least a fair price.

@user3528438, GE doesn't seem to like Boeing that much ... ... all US suppliers hates Boeing ... --- why?

Currently the only engine option for the Comac C919 available is the CFM LEAP high-bypass turbofan. The chinese are currently developing and certifying a domestic engine alternative, the ACAE CJ-1000 high-bypass turbofan engine. However as of today, this engine is delayed by 8 years and is projected to be ready for duty in 2030 (according to Aviation Week & Space Technology). I think it is safe to say that this engine was also their back-up plan, however with this massive delay in development, I speculate that if the US would not deliver engines anymore it would simply halt the development of the C919.
The underlying problem is that engine technology is very complicated and expensive to develop. The chinese are in the process of catching up, but are not done yet. Some good overview can be found in this question.

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From which aircraft does this vintage altimeter come from?
I bought this vintage U.S. Navy Kollsman altimeter at a market in Bangkok, Thailand.

Unfortunately, I don't have any info other than what you see in the photos.

It's a Kollsman altimter and the model or serial number is KO-67ICLU-035 Type/6433 MB-I

There is another serial number(?) on the scale which reads MS28044LI, and below ALT it reads 50,000FT.

Here's another clue: This sticker says the altimeter was serviced in the PNCLA (Pensacola) 89771 NAVAL AIR REWORK FACILITY in the 3rd fiscal quarter of 1981.

Another sticker says it was tested at the Naval Air Rework Facility Pensacola (NARF) and found to be free of radioactivity, also in 1981.

Finally, S/N-71 is embossed on the backside of the altimeter.
So what type of aircraft could this instrument have been part of?

Instruments are often not built for a specific airplane, this could have been used on any number of aircraft.

Yes, I know. I was hoping the stamps would provide some clues. I think we're looking at a U.S. Navy aircraft that has likely been in service in Southeast Asia sometime in the 70s/80s.

I found a manual for it http://www.liberatedmanuals.com/TM-55-6610-247-40.pdf from the U.S. Army. Could this possibly help narrow it down?

The MS in MS28044L1 stands for military standard.

My current guess: https://olive-drab.com/idphoto/id_photos_th55_osage.php. But I have failed to find hard evidence for the U.S. Navy using them.

The fact that it was tested in Pensacola probably doesn’t mean much. NAS Pensacola was home to the Naval Aviation Depot Pensacola until 1993. There were probably a whole lot of maintenance parts from many different aircraft that passed through there.

What you have is a Kollsman C-12 altimeter manufactured by the Square D Company in Elmhurst, New York. The 50,000 FT marking below the Military Standard number means that the altimeter is accurate up to 50,000 feet of altitude but this number might far exceed the capabilities of a particular aircraft as it was universally used on many different types. The free of radioactivity sticker means that this instrument does not have the radium dials found on earlier models (common on WW-2 instruments) or, was later retro-fitted with a non radium face. Since you purchased this instrument in Thailand I am suggesting it came from a T-28 Trojan. The Royal Thai Air Force operated 120 T-28s from 1962 to 1988. The United States Navy ceased T-28 operations in 1984 but by then many of their T-28Bs  had been modified into "Ds" as counter insurgency aircraft and shipped abroad. Since the Thai Air Force recieved all their aircraft from America, there is a excellent possibility that your instrument came to Thailand either in a ex Navy T-28 or as a spare in a support maintenance package.

Well, that seems to make sense. I think the Tango Squadron Museum in Chiang Mai has at least one T-28 on display, so I might as well check it out next time I head over there. And thank you for the info, I appreciate it!

You're welcome, and take your instrument with you to the museum. They might have a a maintenance manual or parts reference index that would help identify your instrument. BTY, the T-28 is a real gentleman's aircraft and a pleasure to fly..

Could you perhaps explain how you came to "as it was universally used on many different types [including the T-28 Trojan]"?

The C-12 altimeter was the one quintessential instrument found on a multitude of aircraft from WW-2 fighters and bombers to more modern aircraft before the advent of the glass cockpit.  Search aircraft cockpits photos and this instrument will be seen in most aircraft except the newer glass cockpits.

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Can a non-citizen get a pilot job in Canada if they have an FAA CPL?
I am an Indian national and considering taking CPL classes in the US. Upon graduation I should have around 250 hours under my belt and FAA licenses. Based on my citizenship status and FAA licenses, would any Canadian airline/general aviation employ me? (This is also assuming that I appear for the Canadian license conversion exam, clear it and have my licenses in order.)
Alternately, if anyone knows any other ways to build hours while in the US (like working as a flight instructor on an F-1 visa) please let me know. I need to build a good amount of hours before I can apply to any major air carrier.
Thanks.

Suggest you go to a site where pilots, not enthusiasts, can answer you questions. Like this one.

It would be like taking any other job in Canada.  If you aren't a permanent resident/landed immigrant, you need to obtain a temporary work visa with job offer in hand.
In Canada you can hire on with a 2nd tier (Regional) carrier with lower hours than the US because there isn't the "Colgan Rule" that requires 1500 hours (US Regionals have complained bitterly about this, because there are situations where they are forced to take inferior candidates because he/she has the hours, and pass on a superstar that is 500 hours short).
The candidate market is becoming very tight.  Air Canada Jazz operates Q400s and CRJs and is taking pick of the litter kids right out of the colleges and puts them through a more comprehensive training program than the normal two-weeks-then-7-sim-sessions-and-a-checkride whirlwind type course, although off the street candidates will need more time.  West Jet Encore runs Q400s and has dropped their 1500 hour off the street requirement for new FOs down to 1000 hrs and is also running a special mentoring program with the colleges.

Thank you for this invaluable information. So, off the top I have two more questions to your answer:

If I were to get a permanent residency for Canada, would there be a problem then, for the regional airlines to employ me?
Does Canada require any other licenses or would my FAA license be enough to apply to the airlines?

No you would have to have the Canadian Commercial, IATRA exam (for multi-crew, basically an abbreviated ATPL exam) complete, and a Group 1 (multi-IFR) instrument rating.  You should be able to get the conversion from FAA comm multi IFR to Can comm Group 1 with just a conversion exam, but I believe you'd still have to write the IATRA.

Ok. So if I apply at a Canadian flight school, get accepted, get my licenses then there ideally shouldn't be any issue in hiring me at a regional airliner, correct? If that is so, then it would make more sense for me to get all my training and licenses in Canada itself. Save me some license conversion stress and money.

If your objective is to live and work in Canada because you want to be in Canada you might as well.  If you already have the funds saved, you might find that although costs are higher, 30K in US funds is 40K in Cdn funds right now so it might work out about the same.  However keep in mind that to fly with a Tier 1 or 2 you would need a Cdn passport which requires citizenship (I imagine the US is the same).

Thanks. My objective to be honest is not to be in Canada or US as such. But recently I learned that US regional airlines won't employ me unless I have 1500 hours, which I won't get until I get a job in general aviation or as a CFI. And thus, I started looking at Canada as an option. Wondering if Canada also has the same flying hours requirement, and if they would employ me as a CFI if I am not their citizen.

As I mentioned in my answer, there is no minimum time like the US, just the required licenses that have their own requirements.  To get a job with low time with a regional you would have to be in one of the colleges they recruit from, and be in the top 10 or 20% of the class.  If you are average you will end up doing it the hard way like most people.  To work in a lower level job that didn't involve international travel, you would just need Cndn licenses and a work visa.

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What are the "Start & Acc" and "Pitch stab" circuit breakers for on the Piper Dakota?
I am learning to fly a piper dakota and I found two circuit breakers for which I can't find an explanation:

Start & Acc circuit breaker. I understand that 'Start' is for the starter. What does 'Acc' stand for?
Pitch stab circuit breaker. I would think that this is related to the electric trim control mounted on the yoke but there is another circuit breaker labeled as 'pitch trim'. So what is this one for?

acc is usually accessories. On a car this is things like the interior lights and cigarette lighter

There are separate circuit breakers each for overhead lights, audio panel, instrument panel etc on this plane. The circuit breaker is a troubleshooting starting point. Why would the manufacturer combine the starter circuit breaker with cigarette lighter circuit breaker? If the cigarette lighter is not working in flight..is it really wise to mess with the starter circuit breaker?

It is for (two) accessories and the starter, they are on the same 15A circuit breaker. The page you want to look at in the POH is Section 7.17 (this is figure 7-11):

I know the image isn't all that clear, but the 15A breaker is on the right side of the alternator buss. It includes the cigar lighter, cabin light and starter solenoid.

Why would the manufacturer combine the starter circuit breaker with cigarette lighter circuit breaker? If the cigarette lighter is not working in flight..is it really wise to mess with the starter circuit breaker?

I'm not sure why Piper put those two things on there, but they did. I don't see it as a problem though. If the cigar lighter isn't working that isn't a problem, you wouldn't mess with the breaker. If it is melting a hole in the dash then yes, you pop the breaker, hopefully you wouldn't need to use the starter in-flight. I would consider the need to pop that breaker (due to heating/smoke) an urgent situation (maybe not emergency, but I'd divert to the nearest airport).
As for the "PITCH STAB", that is probably for an autopilot or altitude-hold system. The Dakota was available with a number of different autopilot options that operate separately from the electric trim system.

This is an outstanding answer. I'm not an electrical engineer by training and intentionally skipped the circuit diagram while reading the POH. Will not make the same mistake again in the future. Many thanks!!

The diagrams in the POH are intentionally simplified so that you don't have to be an electrical engineer to understand them. They are a good thing to know, at least how to read quickly, in case something happens (like the cigar lighter smoking in flight) so you know what breaker to pop. The other method is to pop them all and turn them back on one-by-one until you find the one with the issue, something that can take significant attention away from flying/navigating.


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If a winglet disconnected from an airplane mid-flight, what would be the consequences?
I've always knew that the winglets on an aircraft provide lift. But what would happen if a winglet disconnected from one wing while a winglet was on another wing?

this actually happened to the Rutan around-the-world flight, where one winglet was shaved off against the runway pavement during the takeoff roll. the pilot then stabbed the controls to overstress the remaining winglet, causing it to break off during climbout. the purpose of the winglet is to increase the apparent span of the wing by blocking airflow out from under the wing and over & into the airflow over the top of the wing, so an aircraft with one winglet on and one off would perform as if the wingspans on either side of the fuselage were several feet different.

The pilot was Burt Rutan's brother Dick, and he usually accompanied the mention of winglets with expletives. No wonder he broke them off on purpose.

One a modern airliner, the only conceivable danger would be if it hit any of the tail surfaces on its way down.
A 747-400 is despatchable with one removed but not two (I don't know why). There is also a fuel penalty factor but its nothing major.

It is strange that an asymmetric condition is allowed, but not one with both missing. Do you happen to have a source for that?

I cannot find winglet in MMEL.

Winglets aren't in the MEL but the CDL. The A330 has the same one missing winglet rule. I think the reason is because you need to analyze and flight test the configuration, and having two trucks crash on both sides of the plane isn't a feasible oops.


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Is there a significant difference between the jet blast from Airbus and Boeing?
I am looking up for jet blast data and there are not much information in the net.
One of the main references I can found are the Airport Planning of each aircraft.
From these can be obtained that the jet blast contours from Boeing's aircraft are quite longer than the Airbus's ones at idle and breakaway conditions (the double in length of the jet blast print).
According to this, simulations carried out using specific software (AeroTurn, in this case) show that the jet blast affected area by a breakaway run of a B737-800, for example, would affect stands in a 100 m backwards zone, which is far from the truth.
Some researches can be find Googling a little, but they show comparison between simulations and experimental jet blast data from a JFK test campaign, besides the own JFK data.
Could anyone confirm if the difference is real? A mapping study, an experimental analysis or other similar evidence would be useful.
Thank you everyone for your help, and thanks for all your work in the community.

Did you just look at the pictures or compare the actual data? Maybe/possibly/probably Boeing used a different cutoff wind velocity (e.g.) for their diagrams as compared to Airbus when writing their manuals.

@jwenting, I am using data from the simulation software and from the Airport Planning Manuals of A320-200 (page 275 for CFM56) and B737-800 (page 414 w/ CFM56-7). Links below:
https://www.airbus.com/content/dam/corporate-topics/publications/backgrounders/techdata/aircraft_characteristics/Airbus-Commercial-Aircraft-AC-A320-Feb18.pdf
http://www.dept.aoe.vt.edu/~mason/Mason_f/B737.pdf
The 35 MPH velocity contour for B738 is quite bigger than the equivalent velocity contour for the A322 (15 m/s).
Both cases consider sea level, static and no wind conditions.

@CptReynolds , I have presented the theorical data for B738 and A322 (both with CFM56 engines) in the previous comment.
Anyway, the B738 velocity contour for 56 km/h (=15m/s) extends quite more than 70 meters meanwhile A322 (even with V2500 engine) doesn't reach 60 meters backwards for the 15 m/s velocity contour, according to page 276 of the document linked below:
https://bit.ly/2AP3e3e
In any case, what I am looking is for other documents confirming this difference in the APM data, because with this jet blast, the Boeing could not operate "safely" in most of the airports.

@Aeroturned You’re correct. I must have misread, apologies! Earlier comment deleted.

Based on the observed differences, I would probably adress this question to the manufacturers, to be honest.

Probably not.
Airbus and Boeing aircraft may even have the same model of the engine. For instance,  2.4 m diameter Pratt & Whitney PW4000 is used on Airbus A310-300, A300-600 and also Boeing 747-400, 767-200/300. General Electric CF6-50 is used on both Airbus A300 and Boeing 747.
I would expect much more differences between jet blast from of Airbus A380 versus Airbus A220. A220 is near ten times lighter (575 vs 60 t).

Thanks for your answer, @h22 but, so, if they may have the same engine, why they report in the Airport Planning Manuals different jet blast distance? That's the point of my question.
About the A380 and A220 difference, it is already stated clearly in the manufacturers' documentation.


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What crash does FAA SAIB CE-10-11 refer to?
The Federal Aviation Administration released Special Airworthiness Information Bulletin CE-10-11 on December 23, 2009 advising pilots of what procedures to use when resetting tripped circuit breakers. The background section refers to a crash where the airplane's weather radar system wiring caused a burning smell and the pilot pulled the breaker. When the breaker was reset for the next flight that flight subsequently crashed. I'm curious what flight this bulletin refers to because I'd like to read its associated NTSB report.

It was NTSB accident ID NYC07MA162. A Cessna 310R went down in Florida in 2007, the NTSB information is here and the flight was analyzed by AOPA. The NTSB report has lots of details, the aircraft was owned and operated by NASCAR, who unsuccessfully sued Cessna after the accident.

From the details it sounds like the accident was N501N, a Cessna 310R that crashed on 10 July 2007 (NTSB Summary Report (PDF)).  This airplane had been previously written up for an anomaly with the weather radar and subsequently improperly released back into service.  The accident crew reported smoke in the cockpit and post-crash analysis revealed substantial electrical component damage, burned wire insulation, etc.


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Is it possible for crew oxygen to exacerbate a flight deck fire?
Crew oxygen is, as I understand it, a very high percentage of purity.
Oxygen-enriched air acts as an accelerant to a fire, causing things to ignite which wouldn't in ordinary air, and making fire more difficult to put out. Nice illustration of what oxygen-enriched atmospheres can do to shirts: here, p. 5. This also says that hair and clothes can trap oxygen, and this can be very dangerous. A spill from a mask might well accumulate in hair and clothes.
Also, although I'm not a chemist, it does appear that the margin between normal air and dangerous oxygen-enriched air is quite a slim one: this document says that at over 23% concentration "mixtures must be handled with all the precautions and care of pure oxygen as they start to change fire chemistry and enhance combustion."
In the event of flight deck depressurisation occurring simultaneously with a fire, and the crew using their bottled oxygen, could the following events pose a serious danger:

leak in one of the tubes involved in supplying the oxygen
crew member taking off their mask (and using a portable oxygen supply
instead)
crew member inadvertently pulling an oxygen tube out of its attachment in the course of some bodily manoeuvre
crew member switching their mask to "emergency mode" i.e. where constant pressure is maintained to prevent inhalation of noxious substances, but also perhaps resulting in leaks of oxygen from the mask? (here)

Not an aviation person so don't know how often emergency mode actually gets used, but if the FD were filling with smoke wouldn't you switch to emergency mode to try not to be breathing it in? But could this exacerbate the fire?
Unless my thinking is flawed in some way, wouldn't that mean that descent to an altitude where you no longer have to use oxygen might be quite an important priority in the event of a FD fire? Or maybe blowing an inert gas like argon into the FD*?
Just a final thought: oxygen-enriched fires also burn at particularly high temperatures (Apollo 1, EgyptAir 667). So the danger of such a fire actually destroying navigational or communication equipment and effectively killing the plane might be greater.
* High-concentration argon poses its own danger but for this specific situation, where the crew are on bottled oxygen, it might be OK until the fire was out.

Don't forget that oxygen leaking from the crew emergency supply will be diluted by the ambient atmosphere. If there's a fire on the flight deck the crew will have more to worry about than the effect the relatively small amount of oxygen from their emergency kit will have.

Thanks, yes, I was wondering about relative volumes and dilution. OTOH, because the air in the FD is depressurised in this scenario mightn't the atmosphere become quite oxygen-rich quite quickly? Particularly in the case of a leaking or ripped-out hose.  Also check out the "shirt" link above: specific warnings about how oxygen can accumulate in clothes and hair = pretty likely if oxygen is spilling from a mask.

Hmm, the shirt is stuffed with paper and filled with pure ("saturated") oxygen. No wonder it explodes. Though, it would also burn quite fast in normal atmosphere, and I'm pretty sure, 23% oxygen wouldn't make it explode. And... A person with oxygen in the clothes should go to fresh air and pat their clothes? If oxygen is such a hazard, patting clothes should be the last thing to do, since it could cause electrostatic discharge, which could start a fire...

@sweber Fair points. Wd be nice to know how dangerous oxygen-enriched air really is.


text:
Would mechanical indicators have helped in the Air France 447 incident?
NB I am not an aviation professional.
I saw a documentary about the terrible Air France 447 disaster the other day.
I was struck, as were the experts in it, including David Learmount, who's known as a great aviation expert here in the UK, by the way all 3 pilots were completely unable to grasp what was really happening because of their fatal inability to trust the electronic instruments.
I had a thought: is it not the case when flying any aircraft, whatever its size, that you always need to know, particularly in an emergency, two things?

air speed
attitude

I know this is VERY VERY obvious, but please bear with me.
The fact of the matter is that you can obtain totally reliable information about both these aspects, regardless of darkness, regardless of electronics, regardless of Pitot tubes, at all times:

air speed: by having an incredibly robust, small structure outside the front of the cabin window which would flex visibly according to windspeed, thereby making the invisible (air flow) slightly less invisible: at 0 knots this would be inclined downwards; at over 150 knots the windspeed would cause this to become fully horizontal.  Lack of horizontality would therefore indicate a low speed. One thing I have appreciated since posting this question is the intensely hostile environment this structure would be facing: freezing temperatures, high windspeeds, sometimes containing ice, etc. No doubt one of the reasons why during the development of aviation this has not been considered possible. But materials are being developed now which are much stronger than ever previously known.  One candidate might be carbyne.  It would also presumably have to be heated.
attitude: by having one of those completely mechanical floating compasses (as used on ships) in a prominent position in the cabin. Much confusion has been created in some of the comments about apparent gravity. But apparent gravity has effect only when acceleration other than gravity (down!) and lift equal to 1G (up!) is present. The fact of the plane accelerating/decelerating (in any or all of the 3 dimensions) could be indicated by a system of calibrated inertial accelerometers in all 3 dimensions, with lights varying in intensity according to acceleration.

Obviously such a bendy thingy would have to be very tough to withstand the speeds, battering, temperatures, etc. But it is at least conceivable that this is not beyond the wit of humanity.  Designed carefully, a change in the way it was flexed would then indicate without any possible doubt when an aircraft was in or near a dangerously low speed.
Wouldn't these two measures have had a good chance of providing the pilots of AF 447 with a true and totally irrefutable mental picture of what was actually going on?
PS it has been objected that such a system, even if feasible, would be redundant. But redundancy in critical systems is a desirable thing: what's worrying is if you don't have redundancy, and the aviation industry has made gaffes in the past over insufficient redundancy: Boeing 737 rudder issues; MD80 horizontal stabiliser: "The absence on the McDonnell Douglas MD-80 of a fail-safe mechanism to prevent the catastrophic effects of total acme nut loss" (Alaska Airlines 261, NTSB report quoted).

Imagine the drag from a flag at Mach 0.8...

@Notts90 Are you serious? A small flag, measuring maybe 10 cm in length... and you are worried about the extra fuel bill for that?

Semi-serious. I would imagine over the life of an aircraft that drag would actually cause a noticeable fuel bill. Any disruption to the airflow has a drag penalty that needs to be justified. Also even at that size it needs to be strong and durable enough to withstand the extremely high wind speeds, which a standard one isn't.

A water compass will not serve as an attitude indicator because apparent gravity inside a plane in coordinated flight is always in the same direction relative to the pilots.

The external mechanical indicators you suggest would almost certainly be subject to the same icing problems that brought about the errors in the existing instrumentation.

Ignore the word ‘electronic’ in that report. It's a red herring. They didn't trust the instruments because 1) one failed—in a completely mechanical way—at the beginning of the accident sequence and 2) they were not able to correctly decode the usual combination of indications in the stressful situation. It had nothing to do with the fact the instruments are electronic and everything to do with psychology and some to do with ergonomics of the interface (and electronic interface can be made much more ergonomic—it is just still hard).

@Notts90: you are apparently unaware of AoA vanes which are pretty common on airliners.

@summerrain fully aware thank you.

@Notts90: doesn't seem so at all looking at comments #1 and #3

@summerrain I don’t see your point.

The two crucial elements are not air speed and attitude. They are air speed and stall speed. But since both are variables, which in real-time can only be closely monitored by the electronics, it is difficult to design electronics systems for a situation in which the pilot/s have lost faith in the instrument readings! Multiple redundancy might be a possibility: if you support the pilot such that if one system suffers mechanical failure he is assured of that by comparing it against two normally functioning systems.

Unfortunately, if there had been a jazz band in the cockpit singing "The plane is stalling" it wouldn't have helped. If Moses had been in there carrying a stone tablet newly-carved by God himself inscribed "Pitch down" with a host of angels to help announce it, that would have made no difference.
The unrecoverable problems were in the pilots' brains and in the communication between them, not in the aircraft or the technology.
Once in that state, only a fresh perspective (for example stepping back from the problem, bringing in a fresh person to look at it, using a checklist) is likely to snap those trapped in it out of their spiral: of alarming events, inappropriate reaction, unexpected result of the new inputs, and mounting panic.
It's a common experience in many crafts and disciplines, though in some - like computer programming - it's easier to find the new perspective than in others, such as piloting or surgery.
Anyone who has found themselves in that spiral will be able to tell you that adding more data or new sources of data to the mix rarely help.
It seems reasonable to think that a clear, simple and apparently unarguable piece of evidence would be the way out of such a situation. Unfortunately, in practice, it rarely if ever is, and there is nothing to suggest that in this case it would have been any different - despite compelling intuitions to the contrary.

The human psychology angle is crucial.  But the "semi-reliable mediation" between direct human perception and physical phenomena through the use of electronic indicators, in which the pilots are capable of losing faith seems a huge factor too.  I've read stuff out there which suggests that pilots quite often don't believe the stall indicators, just as I don't believe Microsoft's "help" system when it tells me that the only solution to my minor technical glitch is to reinstall every driver or (why not?) my entire system.

According to what I've read (e.g. http://crankyflier.com/2011/05/31/pilot-error-likely-played-major-role-in-air-france-447-accident/) A330s did not, at the time of AF 447 (I don't know about now) have stick shakers. Also the stick was placed to the right of him and he was in the right-hand seat. Do correct me if this is incorrect.

Re stall warnings with pilots placed in a situation similar to AF 447: https://books.google.co.uk/books?id=fbXlBgAAQBAJ&pg=PA30&lpg=PA30&dq=how+often+are+%22stall+warnings%22+ignored&source=bl&ots=w_eyPzjxxB&sig=SSjY9oi2T4u6ONf6osiE-PDoXa4&hl=en&sa=X&ved=0ahUKEwjz7qzRhrrSAhXBBsAKHZHjDhIQ6AEITDAJ#v=onepage&q=how%20often%20are%20%22stall%20warnings%22%20ignored&f=false

+1 for the jazz band.  The problem was entirely human psychology here, not instrumentation.  Here is a video of a wheels-up landing, the pilots are fixated on getting  down when they are too high and too fast, notice the screaming noise at 30 seconds in?  They didn't, it's the 'gear up' warning.  Mike, you need to read up 'human factors' in aviation because you are definitely suffering from task fixation/confirmation bias, oh, and try the gorilla test

One of the findings was that the pilots were commanding conflicting inputs on the stick and were unaware of the other pilot's opposite inputs (which are averaged together by the flight computer). Another is that the stall warning went quiet due to IAS below a certain minimum - contrary to what one might expect. I don't see how one can argue that the problems were entirely in the pilots' heads.

@mike rodent I've read your comments on this post and they seem rather strong in tone to me. I'm joining the discussion here to hopefully explain to you why your ideas are not going to work as you intended in real life.
The reason for the gap between your proposed solution and other's comment on "it will not work" is that you have a flawed understanding of the underlying physics and aerodynamics. That leads to many of your assumptions being wrong.

First thing first, attitude. You proposed:

by having one of those completely mechanical floating compasses (as
  used on ships) in a prominent position in the cabin

A floating compass can be upright because of gravity. Gravity, when measured as a force, is not absolute; rather, it is relative to your motion. When you're on a roller coaster, you're defining gravity in your own reference frame. When you measure gravity in this scenario, it is impossible to tell if downward acceleration points perpendicularly to the ground. In fact gravity can be pointing up to the sky. You can put tea in a cup and the liquid will never spill, yet you're upside down.
For that reason a mechanical floating device for telling attitude in an airplane is totally useless: you need a gyroscope. It is one instrument the pilots already had and it was functioning on AF 447.
Furthermore, for your information (although it is not related to the question), a mechanical compass will either lead or lag in a turn. You cannot use an ordinary compass to turn an aircraft; if you do, you will never roll out on your desired heading.

For the speed, you proposed:

by having a (fluorescent?) strip/flag, probably metallic, outside the
  front of the cabin window: at 0 knots this would be inclined
  downwards; at over 150 knots the windspeed would cause this to become
  fully horizontal.

What you're describing is not a speed indicator. It does not measure the physical quantity airspeed. Rather, it is an angle of attack indicator, albeit a heavily dampened one.
Outside of the fuel economy and view obstructing aspect, your proposed solution does not really solve the problem you're trying to solve (namely, the pilots do not trust their digital instruments to tell if the plane is above stall speed):

An airplane can stall at any airspeed. You can be travelling at 300 knots and stalling at the same time.
Stall speed varies when flaps and slats are deployed. Your proposed device cannot be adjusted.
Stall speed also varies with the aircraft's load. As you burn fuel, your stall speed is going to change. So does when you load heavy vs load light. Again, your device cannot be adjusted for this change.
Temperature variation will change a metal's flexibility. Therefore your device can only be calibrated to work at one ambient temperature.
Experienced ambient temperature varies with altitude and more importantly, airspeed!
Your device is susceptible to icing.
If your device has a large enough surface area, it may also be susceptible to fluttering.

The pilots already had an angle of attack indicator in the Airbus.

The third point that I wish to mention, is that video documentaries are only faithful to the actual event to a certain extent. They are constructed based on actual events, however if one derive an analysis based on a documentary, it can be wrong because the content of the video are not a word-to-word transcript.
Online articles are even worse. In the aviation community we generally disregard any articles, both online and printed, unless it originates from a trusted source tied to aviation, such as AOPA or NTSB.
The only source you should be using when analyzing aircraft incidents is the official report. It contains a transcript of the cockpit voice recorder, which are the exact words spoken and not an interpretation by film makers and actors. It also contain detailed analysis of the scenario, including interview with other pilots, simulations of the exact circumstances with different flight crew in a flight simulator etc.

Thanks... some of these points are valid.  But not all.  As far as the media source is concerned, the author of this piece, Tim Harford, is a very well-known and very rigorous UK statistician who works for University of Oxford.  I should have mentioned that his credentials were not merely random.  Second, I speak French and have taken a look at the CVR transcript in the original (mainly in French): at 2 h 10 we do indeed see complete confusion about whether they're going up or down.

Secondly, I challenge the idea that this is an "angle of attack" indicator.  How do you come to that conclusion? Are you assuming that if the aircraft is rising/descending that this would influence the deflection of the strip?  But that would depend on its stiffness, surely.  Your points about the extreme conditions influencing the ability to deliver useful info are interesting, however.

@mikerodent yes, that is my point. Rising/sinking would influence the deflection of the strip, as the act of rising/sinking alters the direction of airflow with respect to the airframe (and thus the strip). If you have a drone (or a really strong fan + some wires) you can run your own experiment. You can also ask a separate question either here or on Physics.SE if you are interested in a detailed discussion.

Thirdly, as regards stall speeds, you obviously have a lot of knowledge about this... but I don't think there's any dispute that AF 447's stall speeds were very low, about 100 knots or less, is there?  Final point: if I am permitted for a moment to take no account of the fuel costs due to drag, surely what I'm drawing attention to is the fact that air is transparent.  Something which might assist a pilot to judge the sort of airspeed of this transparent substance is something which is desirable, by essence.

Finally, I know about "apparent gravity" (although not all that much, obviously).  Again (I said this in an earlier comment), when a plane is neither accelerating nor decelerating, a floating compass can help provide a better picture.  In a roller-coaster cup-of-tea situation, the roller-coaster is constantly accelerating and decelerating.  It is not velocity but acceleration which affects apparent gravity, isn't it?

when a plane is neither accelerating nor decelerating how do you know?! That's the problem! When all outside references are not available (e.g. night, cloud), how would the pilots know if I should trust the instrument at this instant? And to further on that, yes from a physics perspective, a plane is constantly accelerating even in straight and level flight with constant airspeed.

Re your last comment: I've tried to understand how this sentence could make sense: "a plane is constantly accelerating even in straight and level flight with constant airspeed".  Are you talking about, I don't know, accelerations due to air turbulence, for example?  If velocity is constant this means there is no acceleration, doesn't it???

@mikerodent, no, a plane is constantly under acceleration due to gravity. Its velocity vector is constantly changing. If it is not, the plane will float to outer space.

Er... I do know gravity is present (!). The point I was making about roller-coaster acceleration and cups of tea (your example) is that the reason your cup of tea can be "falling" upwards is because at that point the car in which you are travelling is subject very momentarily to 2G mechanical acceleration upwards.  A floating compass will work fine in a plane when there is no acceleration (other than omnipresent gravity).  Of course one has a legitimate concern as to whether one can detect acceleration... but for that one might want to think about using inertial accelerometers.

@mikerodent this comment is getting rather long with this discussion, but it appears that you still have some wrong concepts about the physics. Saying "a plane has no acceleration" is plain wrong, I'm sorry to say. You cannot omit gravity from your calculations. You may start a new question either here or on Physics.SE if you wish further explanation on that.

I understand perfectly well that a plane is subject to acceleration of gravity: quite how you can have concluded the contrary is beyond me.  Please reread what I wrote: "other than omnipresent gravity".  How could I possibly have been clearer? I couldn't have.  Furthermore, on the subject of velocity: you say that the "velocity vector is constantly changing" (under the acceleration of gravity).  This is true of a satellite, but given that a plane is small compared to the Earth, and slower, effectively its velocity vector changes only infinitesimally from minute to minute ...

PS A floating compass works perfectly well at sea level... where gravity is present.  Where it is subject to gravity.  Where it is neither rising nor falling, as in a plane flying straight and level where the acceleration due to lift is equal (but opposite!) to the acceleration due to gravity... I give up.

"The pilots already had an angle of attack indicator in the Airbus": No, this was a recommendation of the BEA to evaluate the possibility to have a mandatory one. There are AoA probes, the value is used in normal law to protect the flight envelope, but is lost in alternate law. Besides the AoA measures were invalid from time to time.

A flag is not really effective because a big jets stalling speed is well over 100+ knots. The flag will be blowing fully even in the stall. I'm not familiar with the ship suggestion but it sounds like you're desribing a gyroscope - aka an attitude indicator, which is already right in front of the pilots.
But furthermore, it doesn't solve the problem. AF447 was a very complicated accident. The plane was literally screaming at the pilots that it was in a stall. All of the indications were there for the pilots to identify that they were in a stall. And yet, the pilots didn't recognise it. Putting another indicator would not do anything to solve this.
As a side point, the third pilot (the captain) did recognise the stall relatively quickly, he just wasn't in the cockpit early enough to help.
EDIT: A metallic flag or something stiff may give some indication that airspeed is low, but it's usefulness is still limited. In a fully-developed stall it would point up, which would only confirm that it is descending, not that it is stalling. It also could dangerously impede pilot visibility, such as when identifying traffic in the terminal area.

Wouldn't these two measures have had a good chance of providing the pilots of AF 447 with a true and totally irrefutable mental picture of what was actually going on?

No more so than the standard indicators of attitude and airspeed that we've had for as long as people have been climbing into flying machines.
Attitude indicator

(source: pilotfriend.com)
Airspeed indicator

But that's just the basic instruments - modern airliners have all sorts of other checks/indicators.

In the specific case of AF447 there were other systems to indicate a problem, with the loss of airspeed indicators

The aircraft's stall warning sounded briefly twice due to the angle of attack tolerance being exceeded

Another indicator would have told the pilot that they were climbing too fast

By the time the pilot had control of the aircraft's roll, it was climbing at nearly 7,000 feet per minute

Furthermore, and much like any similar incident, it led to safer aircraft

On 12 August 2009, Airbus issued three Mandatory Service Bulletins, requiring that all A330 and A340 aircraft be fitted with two Goodrich 0851HL pitot tubes and one Thales model C16195BA pitot (or alternatively three of the Goodrich pitot tubes); Thales model C16195AA pitot tubes were no longer to be used.

The fact is, and it's one that is hard to grasp if you've not experienced it first hand, that spacial disorientation is really hard to recognize while in it. Pilots train hard to avoid it, but being humans they make mistakes. No amount of extra telemetry will ever change that.

No, a wind sock would not be effective as a replacement for nor as a backup to the airspeed indicator. What works well at wind speeds we're familiar with in daily life, say 10-30mph, wouldn't be the same at 500 mph.


text:
How are multiple frequencies monitored at once?
In a tiny single-engine aircraft like a Cessna, all the way up to a modern jetliner like a 747, it seems the cockpits of modern aircraft have at least 4 separate airband radios, for monitoring up to 4 different frequencies at once.
However, the cockpit has only one up to (rarely) three occupants wearing headsets.
When Ground calls you and says, "monitor Tower, on 121.65", Tower wants to tell you something from that frequency, but Ground also wants you to stay on their frequency.
By which mechanism are multiple frequencies monitored by one or more (fewer than the number of radios/frequencies) crew members?

all the running cockpit radios are heard at the same time, mixed into the same audio

how to know which transmissions came from which freqs?

switches that cause exactly one of the radios to be "active" in the headsets at once, and the other ones are not heard in the headsets

how to monitor multiple freqs this way, without missing transmissions or switching back and forth so quickly it would be unreadable?

I've looked around, but I can't understand how multiple frequencies are easily monitored at once, without running into the problems I mentioned in my guesses.
So how can a pilot alone, or a pilot with a first officer, listen for their callsign on multiple frequencies at once?

"When Ground calls you and says, "monitor Tower, on 121.65", Tower wants to tell you something from that frequency, but Ground also wants you to stay on their frequency.". No. You can never be under the control of two different controllers at the same time, ever.

Off topic but First Officers are pilots too!

@J.Hougaard my impression from listening to ATC recordings was that there was a significant difference between "monitor " and "switch to " or "call Tower on ", but I'm glad that's cleared up :D

There are a bunch of YouTube videos of a ground controller at Kennedy Airport called Kennedy Steve. If you listen to him directing ground traffic you will frequently hear him direct planes to the takeoff runway and then say monitor tower. It is clear from the context that he wants them to stay with him until they are in line for takeoff, then switch to the tower frequency and wait for takeoff clearance. They don’t need to check in with the tower because the ground controller has already told the tower to expect them. Rather than clutter up the tower frequency, they just listen for their turn.

@Ben usually i've seen "pilot" to mean "pilot in command"; i intended to convey the cockpit has a pilot in command and another pilot, who isn't occupied with flying, but i figured i could shorted PIC to "pilot". thanks, though, i'll take care in the future :)

@JScarry Yep, that's exactly the main source of this question

The claim that single-engine aircraft like Cessnas have up four radios seems quite dubious.  I've flown a number of small planes (and have owned one for a couple of decades), and have yet to see one with more than one radio for voice communication.  (Though they're often set up to be able to quickly toggle between two or more frequencies.)  You also have VORs & transponders, but you don't talk on them.

@JScarry can you link to a video where he says "monitor tower" with the expectation, explicit or implicit, that the aircraft will continue to monitor his frequency as well? That is definitely not standard. An aircraft should be given a frequency change when the transferring controller does not need to talk to them any more; whether the change is a "contact" or a "monitor" depends on what the new controller wants.

@randomhead All of the videos I listened to imply that you stay on ground while taxiing to the runway. Once stopped and waiting your turn, change to the tower frequency but don’t say anything. That’s what is meant by “monitor tower”. They’ll call you when it’s your turn.

@JScarry if you can please link a video that implies that. For example "cross runway 13L then monitor tower" or "monitor tower at the end" or similar. Otherwise the pilot is expected to change frequencies immediately. See the AIM 4–2–3 e.

First let's get rid of some misunderstandings:

Many smaller aircraft have just one single radio.
Being told to monitor a frequency does not mean you have to listen to two frequencies at once. See: Being told to monitor a frequency, when are you allowed to transmit on that frequency? Any controlled flight will always be under the control of exactly one controller, never more at the same time.

Now, as for actually listening to multiple radios at once, that is certainly possible, and quite normal on large airliners. In the cockpit of an airliner there will often be up to somewhere around 10 different audio inputs, each with their own volume control. This can include 2-3 VHF radio, an HF radio, NAV radios, communication with ground crew (pushback/handling), as well as audio from the cabin (the PA) and probably a few others. All these audio streams are merged into one, based on the individual volume controls.
Recently having had the opportunity to join a crew on a flight on the jumpseat, I was quite amazed at how good the pilots were at distinguishing between the multiple audio inputs, even when different people spoke at once. But with practise, it's actually not hard to see how it's done. Each audio channel will have a different "topic", using different key phrases and words. An ATC ground unit will be talking about taxiing, whereas the tower will be talking about taking off and landing. And the cabin PA will be explaining how to fasten your seatbelt to a bunch of passengers not paying attention. And of course then there is the fact that people all have different voices. Sometimes it is easy (a female on one frequency and a male on another) and sometimes it is more tricky, but I have never heard two people with the exact same voice.

And the noise on the line may also be distinct helping to distinguish. Pushback will have the engine noise, tower/ATC will have radio static, Cabine phone will have a microphone with recognizable artifacts...

The expectation is that when ground instructs you to monitor tower, 118.5, you will leave the ground frequency.
If instructed, hold short of 10, then monitor tower, they mean when you are holding short, you should monitor tower.  Except that tower will call you.  If they don't and you think they should have, check in.
Many aircraft have more complex audio panels, and it is possible for one crew member to be talking to dispatch, while another crew member is talking with ATC. That, however, is different from an ATC instruction to "monitor xxx."


text:
Would an aircraft which could go through sound barrier at an over 25 degree climb avoid the sonic boom problem?
I read that the "cone" of the sonic boom is a cone of angle 25 degrees extending from the nose of the aircraft, centred on the axis of the aircraft.
I also read that the English Electric Lightning (and no doubt many another jet since) could break the sound barrier while climbing near-vertically.
If Concorde could have climbed at 45 degrees (or less) when it was accelerating through Mach 1 would that have solved the problems associated with sonic boom over land? The idea being that at that angle the cone would usually not intercept the ground (subject to mountainous terrain).
Edit
Following Bianfable's comment I now see the problem: you have to be at this angle from the point you are just about to hit Mach 1 to the point you get to the ocean ... and climbing at that angle would probably reach your operational ceiling fairly fast (and no doubt the thinner the air the more difficult it is to maintain).
So the obvious thing would be to dip down to, ooh, 2,000 feet as you approach Mach 0.95 and then pivot upwards! (To clarify, I do realise Mach 0.95 is trickier at lower altitudes... and also that it's quite noisy...).
And/or use rocket motors to get to a more satisfactory ceiling, perhaps.

Are you aware that the sonic boom is created continuously above Mach 1 and not just when breaking through the sound barrier?

In fact I wasn't, no. Although it makes sense, since sound has a near-constant speed. But the question still stands... if you can continue climbing at 27 degrees until you get over the ocean... does that work?

When flying at Mach 2, the Mach cone will look like this:

The opening angle of the cone $\mu$ at a given Mach number $M$ is given by
$$ \mu = \arcsin \left( \frac{1}{M} \right) $$
I added the red arrows to indicate the direction in which the wavefronts forming the cone will expand as time passes. The lower one will eventually hit the ground and can then be heard as a sonic boom.
When flying upwards at an angle higher than $90^\circ - \mu$, the cone will never hit the ground. For Mach 2 this would be a climb angle of more than 60°:

The individual waves (grey circles) will still eventually hit the ground, but never more than one circle at a time. The wavefronts forming the cone do not hit the ground anymore, therefore no sonic boom can be heard. Note that the cone only extends backwards up to the moment where the aircraft first reached supersonic speeds and therefore does not continue backwards into the ground (because the aircraft obviously wasn't in the ground when flying).
It goes without saying that Concorde was not nearly capable of climbing at 60°, especially not while flying at Mach 2. The required angle is a bit less when going slower (about 45° at Mach 1.4), but this does not seem to be realistic for any supersonic airliner.

Thanks, this has given me a different perspective to the problem. I have a question though: even with a climb angle of <60°, won't the intensity of the boom phenomenon be mitigated (for those on the ground I mean)? Surely the phenomenon can't be the same between an aircraft climbing and an aircraft which is flying level? Not least because, as these wave fronts "move", mustn't they reduce in intensity accordingly?

@mikerodent Good point, yes, the sonic boom reduces in intensity the longer it travels through air and the higher angle should spread the energy over a larger area, so I would expect reduced intensity.

This is why rocket launches appear to not have sonic booms, but Falcon 9 landings (as well as X-37B) do, and Shuttle landings did.

@Bianfable you're right, I totally got the question wrong, very good answer indeed


text:
Should there be a directive to return to the takeoff runway immediately on a birdstrike at under 4000 ft?
I live in London and I've wondered what would happen if a Cactus 1549-style birdstrike emergency had happened/were to happen here.
We don't have Canada geese in the UK, but I was just wondering whether the report into the Hudson water landing in 2009 addressed the fact that having the Hudson in proximity actually turned out to be an enormous stroke of good luck.
At LHR planes mainly take off to the west because the winds are westerlies most of the time, but whether east or west there is no comparable body of water in event of double engine-loss at low altitude. In the case of a takeoff to the east you'd see the Thames, but that river, although pretty wide, has many many bridges, quite a lot of river traffic, and meanders a lot.
There are no doubt hundreds of other airports where you don't have a large body of water in proximity (a broad, bridgeless river, large lake, sea or something else).
I'm aware that doing a 180-degree turn with no power is very bad news indeed, since you start to lose both altitude and kinetic energy immediately. I'm also aware that total loss of power on takeoff is extremely rare!
But at airports without a resource like the Hudson should the protocol be that in the event of a birdstrike under, say, 4000 ft, after takeoff you immediately turn around to return to the takeoff runway, without even trying to assess the damage? I've watched a few videos about the "lessons learnt" after Cactus 1549, but no-one has ever said this was one of the conclusions, let alone that such a protocol was established.
The reason why I mention London is partly because I live here, but also because it is a huge, extensive city: there are no doubt places where a crash landing might be attempted (including some of our parks), but a takeoff to the east experiencing a Cactus 1549-type emergency would almost certainly result in substantial loss of life on the ground as well as any fatalities of those on board... unless it headed back immediately.

Good question, and ripe for a lively discussion, but I don't think it's quite specific enough for a single correct answer.  I think you have a chance of the question being remaining open if you were to zero in on something specific, perhaps along the lines of your suggested 4000' break point.  I.e. "is there a typical cut-off altitude between low altitude loss of power and high altitude loss of power, and how do emergency procedures differ?"  (immediate forced landing versus restart attempts)  Surmising over potential outcomes on ground impact is pure speculation, and therefore unanswerable.

... holding my VTC for now.  P.S. is your user name a play on Mickey Mouse?  I like it either way!

@MichaelHall Just for the record, I hope my question will be allowed to stand, and that lively discussion is what I was hoping for. Obviously the main focus is on what would indeed happen, with the current directives and training: as I understand it, pilots' training is generally NOT to react precipitately in any situation. Could this be an exception? Yes, my handle is, inter alia, an allusion to my lack of expertise in this and many other domains. PS not sure what "VTC" means... !

Very well then, but if you have been a member here for as long as you have you ought to know by now that discussion is definitely frowned upon.  There are lots of other venues to chat about possible outcomes, but if you won't narrow it to a specific answerable question then I'm afraid I will join with the inevitable votes to close that I anticipate coming along...

OK... I'll make it specific to the 4000 ft idea...

P.S.  VTC=Vote To Close.

"should there be" is opinion based. please ask a question that looks for a factual answer.

The uncomfortable fact is that, after passing v1 and until quite a bit of altitude is gained, a dual engine failure will almost surely result in a severe accident. There's no directive that can prevent this type of accident.

According to Wikipedia, in the US alone there are 13,000 bird strikes each year. That means there have been about 169,000 bird strikes since the Miracle on the Hudson - again, that's the US only. None of those 169,000 flights has met a similar fate. Most would have even continued to the destination, quite possibly not realising the strike happened until they saw blood on the airframe after the flight. There is no need for a directive like you propose.

@Ben That puts it in some perspective, indeed.

@Berend Strange hostility. Have you not understood my question? I was specifically, quite specifically, asking about cities where there are no such open bodies of water.

You cannot develop a directive for each and every type of emergency. Each type of emergency need different response that is difficult to anticipate them all.
Let’s say in case of bird strike in your proposal if you mandate that immediate return is mandatory, what if the engines are running fine and there is traffic behind you? Wouldn’t it more safe to coordinate with ATC for return to airport?
Hence it is best to leave a room to a well-trained captain to assess damage and best course of action to them. Anyway they have excellent training both in theory and flight-sim. Lesson learned from flight 1549 can be added to their training to increase awareness.


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What about measuring airspeed from control surface forces on the framework?
I watch a lot of these videos that people make about air disasters.
One factor that seems (or hopefully seemed) to crop up is where pilots get hopelessly confused about airspeed, particularly (it seems) when visibility is poor, including night-time. This includes Air France 447, and many others.
If a jet flies too fast it will eventually disintegrate. As was the case with Lauda Air 004 (not in any way caused by airspeed indication issues): in that case it was seen that the first thing to disintegrate appears to have been the stabilisers, as the jet accelerated downwards, probably to over Mach 1. I believe that the main force responsible was simply the power of the air on these control surfaces.
Obviously the air exerts forces on the wings, stabilisers and rudder assembly. These forces in turn must exert bending forces at the points where these attach to the aircraft framework. Surely the most reliable way of measuring airspeed (or at the very least another indicator that the computers could use to build up a reliable picture) would be to measure such forces? But I'm not aware that any jet does that. Why not?

AF447 was mainly caused by poor trained pilots and confusing human-machine-interface. Lauda Air 004 by the in-air deployment of a thrust reverser, nobody knows why. In both cases airspeed was not the direct cause of the accident.  "the most reliable way of measuring airspeed would be to measure such forces" have you a source for such claim about reliability?

prefacing your sentence with "surely" gives me the impression that you are sure of it, and are looking for validation. if you're not sure, maybe you can find a different way to convey that? - aside from that, the way the question is structured gives the impression that you think having a better airspeed measurement would have somehow prevented the accidents you list.

There wasn't a problem with inaccuracy in airspeed indications in either accident @mikerodent, in both cases airspeed indications were correct. The current method of measuring airspeed is actually very simple and reliable. In any case airspeed isn't as important as the angle of attack in preventing accidents.

Your assertion that changes in airspeed cause measurable bending where the wings attach to the airframe is deeply flawed.  By the time the wings bend backwards it’s too late, they will have exceeded their yield strength.

@GdD. I mentioned Lauda 004 only to point out that planes eventually disintegrate due to excess air flow, NOT (AT ANY TIME!) to state that airspeed indications were EVER involved (nor was this implied, IN ANY WAY). But you are completely wrong to assert AF447 did not involve airspeed indicators. And airspeed indicators based on bending moment would not have failed under those circumstances.

@mikerodent, I suggest you read the AF447  accident report in detail to correct your understanding of events.

Behind any accident there's a chain of events and all of the rings are needed to get to the final accident and just because there is a start ring doesn't imply that that ring was the weakest.

@GdD I suggest you read the report. The first incident which occurred, without which the plane would not have crashed, was the freezing of the Pitot tubes.

There are very sensitive strain gauges, they are used in flight testing to measure stresses all over airplanes. The problem with your idea is that strain is not a good measure of airspeed, this is due to there being many other factors, for example changes in g-forces. Changes in the angle of attack will change strain without a change in airspeed, and turbulence would have readings varying wildly. Other factors would include loaded weight, the fuel quantity in the wings, and others.
The only way such a system would work would be to take all those data points and feed them into a complex real-time computer model which would determine the airspeed based on the interaction of all those factors. Complexity is the enemy of reliability, using strain to measure airspeed would likely be far less reliable than the current pitot based system.

I was just writing the basically same thing  Yes, I can't also think about a place on the aircraft where deformations are only proportional to airspeed... except maybe on the inside of a pitot tube :-)

Thanks. On the face of it this looks like a powerful objection... but I'm not sure I'm convinced by the reality of the physics. These strain gauges would be measuring strain in the longitudinal direction of the aircraft only. I don't believe the longitudinal forces due to turbulence would ever be comparable to those caused by the forward motion of the plane at 500 mph. I think that similar considerations might apply to other G forces, since their entire aircraft would always be subject to the same G forces.

... and in fact, "longitudinal forces due to turbulence" means one thing, and one thing only: changes in airspeed, which is what one is trying to measure.

@mikerodent, you may have to accept that your idea just won't work.

@GdD Indeed I may, if credible reasoned arguments are put forward showing that it won't work. I haven't seen any yet.

Obviously the air exerts forces on the wings, stabilisers and rudder
assembly. These forces in turn must exert bending forces at the points
where these attach to the aircraft framework. Surely the most reliable
way of measuring airspeed (or at the very least another indicator that
the computers could use to build up a reliable picture) would be to
measure such forces? But I'm not aware that any jet does that. Why
not?

To measure those forces, there would need to be some sort of strain gauge at the point where the structure meets the fuselage.  The problem is that because these anchor points are known to be points of potential failure, they are over-engineered to be extremely strong.  Under normal flight conditions the effect of the forces acting on those points is likely to be unmeasurably small.
The standard method of measuring speed in an aircraft is the pitot-static system, which has proved extremely reliable over the years, from a search for pitot-related  crashes, accidents and incidents on AVHerald.com it appears that the most common issues were insect infestations (as a result of inadequate maintenance after being stored during the Covid pandemic) and bird strikes on the pitot tube.  In most cases pitot problems didn't cause any casualties.
In addition to the pitot system, the aircraft will have a GPS/GNSS system that also displays the speed, the Airbus version is described here:

the speed scale will display the back-up speed information derived
from the angle of attack

Changing from these, or adding a new system to them is unlikely to increase aircraft safety or improve pilot performance.

There IS at least one adult in the room! Strain gauges, exactly! And indeed you may have said exactly what the flaw with my suggestion is. Although, having said that, I am slightly surprised that in 2022 there should not be strain gauges which act almost at the atomic or at least nano level, able to detect incredibly small deflections. I understand about GPS/GNSS (and INS) systems, although as I understand it these cannot measure airspeed, only acceleration, velocity and position relative to Earth (not relative to air through which the plane is passing...).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7922605/ - "nanostructured" strain gauges, limits of sensitivity thereof, etc.

@mikerodent - Whether you can measure at the “atomic” level, one must consider the noise in the environment- buffeting, rain, & also that material stiffness is usually affected by temperature leading to a need for temperature compensation. Also any surface that has control surfaces attached would also undergo stain as those surfaces were deflected- the compensation algorithms would be very complex.All to arrive at a value that would likely be compared to a pitot-static-derived value to prove it was correct. There seems to be a lot of downside and no real upside to this approach.

@Jim Thanks. A similar point was made by GdD in her/his answer. I am not convinced by this point, as the system would be measuring only longitudinal stress, and in reality the forward motion of the plane, and the consequent stresses on the leading edges, would outweigh everything else in this direction. I'm not saying this system would be "better" than Pitot tubes, rather that the longitudinal strain is clearly a pure function of the force caused by the on-coming air. We can be certain that birds do not have Pitot tubes, but clearly they must sense the strain on their wings.

@mikerodent - Yes, but as an elevator deflects upward or downward it not only produces a moment about the pitch axis it also increases the drag along the longitudinal axis. This will also be measured by the strain gauge. And it would not know whether this was from increased airspeed or control deflection.

Just as you don’t have a pitot but can judge how fast you’re going based on the wind in your face. But I would posit that you aren’t judging that by the strain in your neck muscles but by the pressure hitting your face- much more akin to a pitot tube than a strain gauge.

@Jim good point about the elevators, which also applies to the other control surfaces, such as the flaps and the rudder. However, the degree to which this would influence the drag would also be, like the strain produced longitudinally by the airflow, a pure, i.e. completely predictable, function of the commanded changes to geometry. This would of course increase the complexity of the measurement function but not by much.

@Jim you're right about the wind in the face being equivalent to Pitot tubes. But I didn't mention faces, I mentioned how birds sense motion through air in their wings: it is obvious that the faster they fly the greater the exertion they will find themselves having to make with their muscles to keep their wings functional. That is a function of the strain caused by airflow. I don't know whether any research has been attempted on this subject, but I surmise that a bird can measure windspeed more accurately by muscle strain than by (e.g.) hairs in their nostrils (functioning like Pitot tubes).

PS obviously the latter observation does not apply when a bird's wings are folded back and it is in "plummet" mode (I include this remark because I have an uncanny sense that someone in this forum might think they had found a "gotcha" with this point!).


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What are the major causes of parachutes failing to work?
What are the top causes of a parachute failing to work?
For "parachute", I mean primarily sporting parachutes, such as used in skydiving, but information about military (paratroop) chutes, ejector seat chutes, etc., would be useful.
For "failing to work", I mean "fails to prevent the sudden stop at the bottom", whether this is through failing to deploy properly, getting tangled, structural failure or whatever.

Inspired by the following comment on this answer:

maybe you could add something about why sometimes chutes don't open. –  rbp

While the source is highly suspect (SFC Jackson had a tendency to embellish for dramatic effect), I recall that an (Airborne by trade) instructor at my avionics school in Ft. Eustis would often remark on the army's chute-rigger MOS being the most statistically prone to test positive for drug use during random screenings. It would seem that wikipedia, at least, has nothing to say on the subject, though. It was probably just talk.

Hello - your Friendly Neighborhood Parachute Rigger here.
Sport chutes are pretty reliable, have been since the mid 90s to the point where more accidents happen under fully functional canopies.
If we disregard rank stupidity like tying the flaps shut1 or incompetent packing we find that the leading cause of malfunctions is bad body position on deployment. You are supposed to be face down, shoulders level before opening the thing. If you are on your back or tumbling you can have various parts wrap around you. High-performance canopies are somewhat more sensitive to the shoulders being level and can open in a decently fast spin. Depending on the spin direction and your altitude you may not be able to recover2.
The emergency chutes are built differently, emphasizing (obviously) reliability over being able to land at 100km/h. This means that twisted lines are either recoverable or not an issue.
If the jumper isn't paying attention to where he is, you may find that a leading cause of going splat is not using the perfectly good canopy on your back. Automatic activators have more-or-less eliminated this as a common cause3, but if the jumper thinks that the houses look a bit too big and deploys the main at the same time as the reserve opens they may decide to wrap each other up. Ram-air canopies are like badgers - they don't like each other very much and having two open at the same time is a rather delicate situation.
If we turn to landing accidents, we find that there are all kinds of ways to injure or kill yourself with a fully functional canopy overhead. The aforementioned 100km/h landing speed is no joke - hit an obstacle on the ground going that fast and it's exactly the same as jumping out of a car on the highway. Buildings, trees, power lines, vehicles, running propellers etc. have all claimed their sacrifices. And don't try to land on both sides of the fence at the same time. Or in the alligator farm across the road.
Mechanical failure of the system is very rare - riggers won't pack worn-out reserves, and if they are concerned about someone's main they will tell the dropzone management who will usually decline to provide services until it's fixed.

Many jumpers will tie various handles to the pack before travelling. Prevents the pack accidentally opening when curious security or customs pick it up by what looks like the carry handle. Remove before Flight!
Happened to me twice - the first time I looked up, then down, decided I didn't have enough time to fix it. The second time it was spinning the other way and I fixed it in 2 seconds.
Automatic activators fire at 750-1000 feet. If you are in freefall below that altitude you're usually done.

I heard of highly experienced parachutist with a camera pack died even though his parachute seemingly worked normally- he just landed badly so the failure standard of a sudden stop means any parachute landing could be considered a faulty one.


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In calm winds, which runway should I select at an untowered airport?
In calm wind situations, approaching an uncontrolled airport with no other aircraft reporting on CTAF, which runway should I select that would cause the least safety hazard?
Especially at an airport with one runway, I don't want to set up to land head-on with an aircraft flying without a radio.

Often uncontrolled fields will publish a preferred calm wind runway in the Airport/Facility Directory. When one isn't published the calm wind runway is usually the longest runway, which gives you a 50/50 chance at guessing right.
To further reduce your likelihood of winding up face to face with another arriving aircraft you should self-announce on the CTAF and overfly the field to observe the traffic pattern. Also, turn on all the external lights 5 miles out. If there is traffic in the pattern you should work yourself into the same pattern everyone else is using.
If the pattern is empty my personal practice is to pick the approach to the longest runway with the fewest obstructions, and ideally one that doesn't overfly residential areas (where it's practical to avoid doing so).

Where I learned, it was land on 13 and take off from 31 because there was nothing but waste land out west. (EFATO options off 13, according to our CFI: "Lan' in de shanty town an' get yu ass shot, drown yuself in de 'arbour, or go cre-mate yuself in de oil refinery.") Making all the calls, getting nothing back, then having a Trislander appear out of the haze at 3 miles and switch the landing lights on just as you rotated was... character-building.

You can talk about obstacles and runway lengths and not flying into the sun and all sorts of other minutiae that probably don't apply in calm conditions in a Cessna 172.
At some point you've decided that there's no one in the pattern, but you're going to keep looking for traffic throughout the pattern just like you learned from your CFI, and you have to pick a runway.
For me, I'll pick the one that requires the least amount of flying, just like the Hawker 800 pilot will do.
I realize that this technique is not for everyone, but if I'm heading southbound, and there's a nice N/S-ish runway, I'll make that straight in, just like it says in this AOPA article:

Straight-in approaches are always a topic for discussion. Under VFR
  conditions they are acceptable only if there is no conflict with other
  traffic.

If I'm heading southbound, and there's an E/W-ish runway, I'll enter a long L or R base, regardless of which way traffic pattern is. If I care about the traffic pattern for some reason (obstacle or noise abatement), I'll make an overhead entry, which means overfly the airport and enter left or right downwind.
If you're uncomfortable with a straight-in, base, or overhead entry, look for the runway where you can make a downwind or 45 entry with the least amount of maneuvering for L or R traffic as per the chart:

In regards to traffic avoidance, unless the airport has a preferred calm wind runway, there's not really a hard and fast rule for which runway you should choose.
However, as you're approaching the airport, you should be looking for traffic both in the pattern and on the field. If there's traffic already in the pattern for a given runway, join that pattern. And, of course, if there's traffic on a runway, don't set up for the same runway in the opposite direction.
Once you've selected a runway, continue to keep your eyes open. You should have a view of the runway for most of the pattern, so you should be able to see if someone without a radio also happens to not look out his window and lines up for departure on the opposite runway. While, as the arriving traffic, you should have the right-of-way over departing traffic, you'd obviously want to break off your approach if the runway is occupied.


text:
Why aren't thin, delta-shaped wings used for fighter aircraft?
In the past, we used thin, delta-shaped wings (ogival wings) such as those on the Concorde.
These wings can be used up to mach 2.2. Due to high fuel consumption, these wings are no longer used commercially.  However, why can't they be used on fighter aircraft?

If you go to the images link on this google search, you will see there are a lot of fighter planes that do use this design (if I understand your question correctly): https://www.google.com/webhp?hl=en#hl=en&q=fighter+planes+with+delta+wings

fighters need to be maneuverable over fast.

Aircraft design is a compromise. What seems important evolve in time. In the past, speed over mach 2 were important, today it is less important than having a polyvalent aircraft with a good maneuvrability both at low and high speed.

Yes, it is. It was used on 2nd generation designs already mentioned by habu, and it is returning now in the 4.5th generation, now with canards:
Eurofighter Typhoon:

JAS-39 Gripen:

Dassault Rafale:

And occasionally without too:
HAL Tejas:

And most of the other designs, while having horizontal tail surfaces, are not really far from that layout either:
Mig-29 (Su-27 looks very similar and all the newer Russian fighters are derived from either of those two):

F-18 Hornet:

The F-22 and F-35 with their negative sweep trailing edge are more of an exception, their layout being governed more by requirement for lower radar cross-section than aerodynamics.

F-22 and F-35 wings are considered trapezoidal, not delta. And I read somewhere (some magazine I think) that trapezoidal wings have better aerodynamic performance, especially in high alpha. They cause less drag.

The delta wing was, in fact, very widely used in fighter designs of the mid-late 50s, 60s, and early 70s. The Mirage series (even the latest models) and their derivatives, the MiG-21, the F-106, and the A-4 are some of the more iconic designs to have used the wing.
However, as time went on, shifting philosophies on aircraft design, along with technological and manufacturing advancement meant that the speed and acceleration attainable with Delta wings could be reached by other means and manufacturers were free to work with other types of wings that don't suffer from the Delta's weaknesses.

Mirage series, F-106 and A-4 are all true deltas without horizontal tail. But MiG-21 has horizontal tail. If you count that as delta, you should count almost all fighters.

@JanHudec - i've always understood the "delta" moniker to refer primarily to the wing, regardless of the stabilizer configuration. Your point, however, does stand in that even after many designers moved away from the classical tailless "delta" configuration, "cropped deltas" and certain elements of the "delta" configuration still show up in a lot of the 3rd, 4th, and 4.5 gen fighters.

Actually, 4.5 gen fighters returned to classical tail-less deltas. A bit cropped so they can have wingtip hardpoints, but they are deltas.

Taking what has already been said and talking it in a different direction…  All military equipment design goes through an evolution based on who you think your enemy is, how you think they might attack you, and the systems and tactics with which you intend to counter that attack.
There was a time when having the fastest possible interceptors produced the best possible likelihood of intercepting an incoming bomber before it posed a nuclear threat to a populated or strategic area.  But many thinkgs have changed.

The era of the overhead strategic bomber dropping a nuclear gravity bomb over its target is gone.  Changing the role of the bomber profoundly changes the role of the interceptor, which profoundly changes the need for maximum speed.

The role of the cruise missile has changed the way bombers deploy weapons.  even my fastest interceptors will likely arrive just in time to find an empty bomber.

The attack role—whether that is a tactical attack or a deep strategic strike, has become much more important in military planning, and that often means low radar observability is far for important than speed.

Radar and satellite capabilities to detect (and more importantly confirm) enemy bomber launch sequences has improved to the point where I have more time to get to interception points.  I may know your bomber has taken off hours before it first encounters my surveillance radar.

The role of the anti-aircraft missile, and the performance of those missiles has evolved, in terms of speed, autonomy, threat resistance…  My interceptor can launch from farther away, subs or missile cruisers can be placed strategically in times of escalating tension, etc.  Land-based SAMs have evolved profoundly.

The likelihood of a strategic conflict and its unique need for interception has largely given way to the much higher likelihood of a very different kind of war.  The US and Europe have shifted priorities away from prioritizing border aerial interception and toward global force projection, in the form of robust attack capability.

This list could keep going, and if we brainstormed, we’d come up with at least 5 or 6 more reasons why the mission of bomber interception has changed in a way that has relieved some need for speed.  Put all these reasons in a blender and they all contribute to a change in aircraft design.